The present invention relates to improvements on a television receiver (TV set) of the type in which a picture is displayed using a liquid crystal display panel.
One of the known liquid crystal display devices employs, for display of a reproduced picture, a liquid crystal display panel with a reflecting plate on the reverse side, as shown in FIG. 1 and disclosed in U.S. Pat. No. 4,403,216. The display panel is able to display a picture in a bright place, but unable to display it in a dark place. The display panel uses the same surface for both incident light and picture display purposes. This structural feature makes it difficult to see a displayed picture. To cope with this problem, another type of liquid crystal display device, as illustrated in FIG. 3 and disclosed in U.S. Pat. No. 4,403,216, was developed. In this display device, a picture on a transparent liquid crystal display panel is projected onto a reflecting plate disposed so as to slant with respect to the liquid crystal display panel. Lights, containing picture information emitted from the display panel, are reflected by the reflecting panel for providing a visual presentation of the reproduced picture to a viewer. Structurally, a housing houses both the display panel and the reflecting plate, thus eliminating the difficult-to-see problem due to the reflection. A spot light, as a light source, illuminates the display panel to solve the problem that the picture displayed can not be seen in a dark place.
However, the spot light illumination method nonuniformly illuminates the display panel. Then, the picture on the reflection plate is uneven in brightness. Inevitably, the picture displayed in a dark place has an uneven brightness. The spot light illummination method, when applied for a transparent liquid crystal display panel of the dot matrix type, remarkably deteriorates the contrast of the picture displayed on the display panel. The reason for this is that this type of the display panel is used at a high duty cycle. For displaying a motion picture, a satisfactory brightness and a high contrast are required. Therefore, the spot light illumination method provides only a poor picture. In this respect, it was very difficult to apply the liquid crystal display device to a TV set. This is also true for color TV application. The color TV requires higher brightness and contrast. Nevertheless, increased loss of light due to light absorption by color filters rejects heightening of the contrast, which is for obtaining a satisfactory tone on the picture displayed.